Control device for internal combustion engine and control method for internal combustion engine

Abstract

A control device for an internal combustion engine includes an electronic control unit. The electronic control unit is configured to control an injection amount and an injection timing of fuel to a target injection amount and a target injection timing set based on an engine operation state, detect an ignition timing of fuel based on a vibration component of an engine body in a specific frequency bandwidth, and correct at least one of the target injection amount and the target injection timing based on a deviation between the detected ignition timing and a target ignition timing according to the engine operation state. The specific frequency bandwidth is a bandwidth on a low frequency side of a frequency bandwidth where the engine body undergoes elastic vibration.

What is claimed is: 
     
       1. A control device for an internal combustion engine including an engine body, a fuel injection valve configured to inject fuel into a combustion chamber of the engine body, and a vibration sensor configured to detect vibration of the engine body, the control device comprising an electronic control unit configured to: set a target injection amount and a target injection timing based on an engine operation state; control an injection amount and an injection timing of fuel to be injected from the fuel injection valve to the target injection amount and the target injection timing, respectively; detect an ignition timing of fuel based on a vibration component of the engine body in a specific frequency bandwidth, the specific frequency bandwidth being a bandwidth on a low frequency side of a frequency bandwidth where the engine body undergoes elastic vibration, and the specific frequency bandwidth being a bandwidth where a ratio of a combustion vibration component that is generated when the engine body is subjected to combustion pressure to vibration components detected by the vibration sensor becomes equal to or greater than a predetermined value; and correct at least one of the target injection amount and the target injection timing based on a deviation between the detected ignition timing and a target ignition timing according to the engine operation state, wherein the specific frequency bandwidth is a frequency bandwidth of 0.1 kHz to 1.8 kHz. 
     
     
       2. The control device according to  claim 1 , wherein the specific frequency bandwidth is a frequency bandwidth of 0.2 kHz to 0.8 kHz. 
     
     
       3. The control device according to  claim 1 , wherein the electronic control unit is configured to make the specific frequency bandwidth narrower when an engine rotation speed is higher. 
     
     
       4. The control device according to  claim 1 , wherein:
 the electronic control unit is configured to calculate a vibration level of the engine body based on the vibration component of the engine body in the specific frequency bandwidth; 
 the electronic control unit is configured to calculate a mechanical vibration level of the engine body based on the engine operation state; 
 the electronic control unit is configured to subtract the mechanical vibration level from the vibration level to calculate a combustion vibration level; and 
 the electronic control unit is configured to detect, as an ignition timing of fuel, a timing at which the combustion vibration level becomes equal to or greater than a predetermined combustion determination threshold. 
 
     
     
       5. The control device according to  claim 4 , wherein:
 the electronic control unit is configured to specify, based on a waveform of the combustion vibration level at each crank angle simplified using a plurality of thresholds, a principal vibration portion when fuel for generating requested torque is combusted; and 
 the electronic control unit is configured to detect, as an ignition timing of fuel, a timing at which the combustion vibration level becomes equal to or greater than the combustion determination threshold in the principal vibration portion. 
 
     
     
       6. The control device according to  claim 4 , wherein:
 the electronic control unit is configured to control the injection amount and the injection timing of fuel to be injected from the fuel injection valve such that fuel causes premix charged compressive ignition in an operation region on a low load side and fuel causes diffusive combustion in an operation region on a high load side; and 
 the electronic control unit is configured to, when fuel is combusted by premix charged compressive ignition, make the combustion determination threshold smaller than when fuel is combusted by diffusive combustion. 
 
     
     
       7. The control device according to  claim 4 , wherein the electronic control unit is configured to correct the combustion vibration level based on a moving average value of the deviation for a short period and a moving average value of the deviation for a long period. 
     
     
       8. A control method for an internal combustion engine including an engine body, a fuel injection valve configured to inject fuel into a combustion chamber of the engine body, and a vibration sensor configured to detect vibration of the engine body, the control method comprising: setting, by an electronic control unit, a target injection amount and a target injection timing based on an engine operation state; controlling, by the electronic control unit, an injection amount and an injection timing of fuel to be injected from the fuel injection valve to the target injection amount and the target injection timing, respectively; detecting, by the electronic control unit, an ignition timing of fuel based on a vibration component of the engine body in a specific frequency bandwidth, the specific frequency bandwidth being a bandwidth on a low frequency side of a frequency bandwidth where the engine body undergoes elastic vibration, and the specific frequency bandwidth being a bandwidth where a ratio of a combustion vibration component that is generated when the engine body is subjected to combustion pressure to vibration components detected by the vibration sensor becomes equal to or greater than a predetermined value; and correcting, by the electronic control unit, at least one of the target injection amount and the target injection timing based on a deviation between the detected ignition timing and a target ignition timing according to the engine operation state, wherein the specific frequency bandwidth is a frequency bandwidth of 0.1 kHz to 1.8 kHz.